There is currently no biologic or demographic predictor of suicide risk that is better than a history of previous attempts. The purpose of this research is to evaluate a possible marker for risk of suicide or other serious psychiatric morbidity. There is evidence that successful suicides, as well as some patients with alcoholism and affective disorders, have deficient serotonergic function. It has been difficult, however, to find a satisfactory, clinically available indicator of central serotonergic regulation. Tryptophan transport is a limiting factor in serotonin synthesis, and there is evidence implying that it is abnormal in affective disorders. In our preliminary studies, we have developed an assay for tryptophan transport rate into human platelets. The transport system in platelets appears similar to that in brain synaplatelets. The transport system in platelets appears similar to that in brain synaptosomes. In this research, we will study tryptophan transport as an indicator of psychiatric risk. This will be compared to platelet imipramine binding and monoamine oxidase activity. The patient groups studied will include violent suicide attempters, nonviolent suicide attempters, nonpsychiatric trauma patients, depressed patients, and age and sex matched normal subjects. Follow-up studies will be performed in order to determine whether any differences found are related to stress or otherwise state-dependent. Patient evaluations will also include demographic data, Research Diagnostic Criteria - DSM-III diagnoses, and symptom ratings. The different patient groups will be characterized using this data and clinical characteristics which differentiate violent suicide attempters will be formulated. These studies will attempt to define a convenient peripheral indicator of serotonergic regulation and psychiatric risk.